1. Field of the Invention
The present invention relates generally to an internal combustion engine control method and more specifically to a control method wherein a control schedule or schedules are updated so as to accurately reflect the current state and individual characteristics of the engine.
2. Description of the Prior Art
FIG. 1 shows an engine system disclosed in Japanese Patent Application Provision Publication No. Sho 57-185501 published on Nov. 15, 1982. In brief, this arrangement includes a central control unit 1 including a microprocessor (comprising a CPU, RAM, ROM, an input interface and an output interface), a battery 2, a starter motor 3, an ignition key switch 4, an induction manifold 5, a throttle valve 6, an air flow meter 7, a throttle switch 8 which outputs a signal indicative of the throttle valve 7 being closed (i.e. idling position), an induction manifold pressure regulator arrangement which includes electromagnetic valves 10, 11, an EGR valve 12, (the vacuum chamber of which is controlled by the aforementioned electromagnetic valve 11), a by-pass control valve 13 which controls the amount of air by-passed around the throttle valve via passage 14 (and thus the idling speed of the engine), a fuel pump 15, a fuel pressure regulator valve 16, a fuel pump control relay 17, a fuel injection valve (or valves) 18, a coolant temperature sensor 19, an exhaust manifold 20, an oxygen sensor 21, a crank angle sensor 22 which produces both a unit angle signal and a reference signal, an ignition coil 23, a spark plug (or plugs) 24, a transmission 25 (of the stepped plural forward speed type), a transmission neutral position indicating switch 26, an air conditioner switch 27 (for indicating the air conditioner being in use), a vehicle speed sensor 28, an alarm lamp 29 for indicating abnormal conditions and a fuel flow meter or the like 30 which indicates the amount of fuel being consumed by the engine per unit time.
The central control unit 1 receives a plurality of inputs and uses one or more control schedules stored in the ROM of the microprocessor to control the fuel injection, air-fuel ratio of the mixture fed to the combustion chambers, the EGR rate, idling speed etc., in a manner to minimize the fuel consumption of the engine while maintaining adequate power output and desired levels of exhaust control.
However, as the schedules via which the engine is controlled are fixed, a drawback is encountered in that the dimensional variations which occur from unit to unit during production of a number of engines (e.g. mass production) and the wear which occurs with the passing of time and which varies with the manner in which the engine is treated, the desired optimal performance is in fact not achieved due to the inability of fixed schedules to take into account the aforementioned unpredictable variations.